The Most Intense Dive

How do we decide where to dive on an island we know next to nothing about? Our approach: Dive everywhere—or at least as much as possible—all around the island! Fisheries ecologist Alan Friedlander consults a satellite map with geographic coordinates and plots points just over half a mile (one kilometer) apart. The larger the island,...

April 11, 2009

How do we decide where to dive on an island we know next to nothing about? Our approach: Dive everywhere—or at least as much as possible—all around the island!

Fisheries ecologist Alan Friedlander consults a satellite map with geographic coordinates and plots points just over half a mile (one kilometer) apart. The larger the island, the more dive sites we will visit in order to obtain a representative picture of the ecosystem. For example, we plan to dive at 27 sites around Malden, while at the smaller Flint we only dived at 14 sites. Every team has a handheld geographic positioning device (GPS) with the coordinates of each selected research site. In the morning, we distribute the sites among the different teams, and off we go!

Our second dive of the day took Alan, Jen Caselle, and yours truly to the southeast corner of Malden. That point has a shallow coral terrace that extends for hundreds of meters offshore. This is a site where we would expect very strong currents, great productivity, and many fish, including grey reef sharks.

And so we found it. On our way, fifteen bottlenose dolphins greeted us and joined the ride. Before we jumped in the water, we already saw a couple grey reef sharks circling the Zodiac boat. As we jumped in, a few more came to check us out. Once we reached the bottom, there were a dozen. After five minutes, we were surrounded by 30.

Alan and Jen were counting fish while I took photographs. We could hear the underwater chirping of the dolphins, which seemed quite excited by our company. Probably none of these animals had seen humans before! Then the dolphins dived near us, swimming fast as torpedoes, and disappeared. And so did the sharks.

I have already experienced something similar on a couple of occasions. It seems that sharks are uncomfortable with the presence of the much more intelligent dolphins. But only a few minutes after the dolphins had left, the sharks returned.

One grey reef shark was especially conspicuous: It lacked a dorsal fin, possibly because the fin had been cut off. We saw this shark throughout our dive. Photographer and diver Mauricio Handler told us later that he saw the same shark shortly afterward at a site three nautical miles (five and a half kilometers) distant. This was an interesting observation, suggesting that grey reef sharks could travel extremely fast and be attracted to a human or ship presence from miles away.

Unfortunately, curiosity kills the shark: We humans have become far too efficient at removing these predators from the ocean. Do you know how many people sharks kill each year versus the number of sharks we kill? According to a University of Florida tally, shark attacks claimed four human lives worldwide in 2008. By credible scientific estimates, people kill close to 40 million sharks in a typical year, mostly for their fins and as bycatch caught in pursuit of other fish.

P.S.: It’s almost midnight, and I am on the upper deck of the Hanse Explorer sending this blog entry with our portable satellite antenna. A perfectly bright moon sheds a delicate reflection on the calm, dark sea. I feel fortunate to be here, but also to be your eyes in this remote and exquisite part of the world.

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Meet the Author

Enric Sala

Marine ecologist Dr. Enric Sala is a National Geographic Explorer-in-Residence who combines science, exploration and media to help restore marine life. Sala’s scientific publications are used for conservation efforts such as the creation of marine protected areas. 2005 Aldo Leopold Leadership Fellow, 2006 Pew Fellow in Marine Conservation, 2008 Young Global Leader at the World Economic Forum.